JP2008175730A - Apparatus for measuring speed of mobile station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for measuring a speed of a mobile station capable of reducing the period when the speed cannot be measured by a GPS and can measure the travel speed of the mobile station even if cycle slip occurs. <P>SOLUTION: A first speed measuring means 23 fuses the Doppler speed determined based on Doppler frequency Da from a positioning means 22 and an integral speed obtained by integrating acceleration at the optimal mixture ratio according to the difference between them, and measures travel speed V1 of the mobile station. A second speed measuring means 25 measures travel speed V2 of the mobile station by a TD (Time Differential) method based on the position Db of the mobile station from the positioning means 22. A switch control means 24 performs switch control so that travel speed V1 is measured by the first speed measuring means 23 after the occurrence of the cycle slip and in the initial stage of restoration from the cycle slip, and travel speed V2 is measured by the second speed measuring means 25 when cycle slip does not occur. This control reduces the cleanup period of the speed measurement. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mobile station speed measuring apparatus that receives a carrier wave transmitted from four or more GPS satellites and measures a traveling speed of the mobile station based on data included in the carrier wave.

When a mobile station equipped with a receiver that receives a carrier wave transmitted from a GPS satellite is moving, there are shielding objects (such as natural objects such as mountains and trees, buildings, tunnels, bridges, etc.) between the GPS satellites. If there is a construction such as), a carrier wave cannot be received temporarily and a cycle slip occurs. Since accurate positioning cannot be performed when this cycle slip occurs, an example of a technique for detecting the occurrence of the cycle slip is disclosed (see, for example, Patent Document 1).
JP 2006-220512 A

  However, even if the occurrence of cycle slip can be detected, the traveling speed of the mobile station cannot be measured by the TD (Time Differential) method or the like as long as the carrier wave cannot be received. Even if reception of the carrier wave can be resumed, a recovery time (for example, 6 seconds to 10 seconds) until the measurement error falls within the allowable range is required. Therefore, there is a problem that a period during which the traveling speed of the mobile station cannot be measured occurs due to the occurrence of cycle slip. Although a method of obtaining the traveling speed by integrating the acceleration during a period in which the carrier wave cannot be received due to the cycle slip can be considered, the integration error becomes large due to the long recovery time from the cycle slip, which is not practical.

  Further, in order to detect the presence or absence of cycle slip, the technique of Patent Document 1 performs a large amount of arithmetic processing (such as obtaining an approximate value by the least square method). If there is a large amount of arithmetic processing, it takes time to detect, so that there is a problem that it is not possible to shift to processing after detection.

  The present invention has been made in view of such points, and even if a cycle slip occurs when the mobile station is moving, the time during which the speed measurement by GPS is not possible can be reduced compared to the conventional case. It is an object of the present invention to provide a mobile station speed measuring device capable of measuring a traveling speed.

(1) Means for solving the problem (hereinafter simply referred to as “solution means”) 1 includes a receiver for receiving a carrier wave transmitted from four or more GPS satellites, and is included in the received carrier wave. A mobile station speed measuring device for measuring a traveling speed of a mobile station based on data, wherein positioning means for obtaining and outputting a Doppler frequency and a position of the mobile station based on data included in the carrier wave, and Observation update data and time update according to the difference between the Doppler velocity calculated based on the Doppler frequency output from the positioning means (that is, observation update data) and the integrated velocity obtained by integrating the acceleration (ie, time update data). A first speed measuring means for measuring the traveling speed of the mobile station by fusing data with an optimal mixing ratio (for example, Kalman gain), and a mobile station output from the positioning means; Second speed measuring means for measuring the traveling speed of the mobile station based on the position by the TD (Time Differential) method, and when the cycle slip occurs, the acceleration measured by the acceleration sensor is updated by the Kalman filter during the occurrence of the cycle slip. In addition, noise filtering is performed to measure the traveling speed of the mobile station. In the initial stage of recovery from cycle slip, the traveling speed of the mobile station is measured by the first speed measuring means, and then the accuracy reduction index is a predetermined value. The gist of the invention is that it has switching control means for performing switching control so as to measure the traveling speed of the mobile station by the second speed measuring means.

  Compared with the TD method, the period from when the cycle slip occurs until the Doppler frequency is obtained is significantly shorter (for example, 0.2 second to 4 seconds). According to the solving means 1, the switching control means switches between the first speed measuring means and the second speed measuring means depending on whether or not a cycle slip has occurred. In particular, when a cycle slip occurs while the mobile station is moving, the first speed measuring means fuses at an optimal mixing ratio according to the difference between the Doppler speed and the integral speed obtained by integrating the acceleration. Measure the running speed of Therefore, even when a cycle slip occurs, it is possible to measure the traveling speed of the mobile station by reducing the time during which the GPS carrier wave that cannot measure the TD positioning value or the Doppler speed from the GPS satellite is unavailable.

(2) The solving means 2 is the mobile station speed measuring device described in the solving means 1, wherein the switching control means obtains an accuracy decrease index related to the arrangement of GPS satellites, and the accuracy decrease index is a predetermined value or more. Switching control is performed so that the traveling speed of the mobile station is measured by the first speed measuring means, and the traveling speed of the mobile station is measured by the second speed measuring means when the accuracy reduction index is less than a predetermined value. The gist is to do.

  The accuracy degradation index is an index related to the arrangement of GPS satellites, and includes a position index (PDOP), a horizontal accuracy index (HDOP), an altitude index (VDOP), and a time index (TDOP). Of these, the position index (PDOP) is most suitable.

  According to Solution 2, since the accuracy reduction index is obtained by calculation based on the approximate distance or pseudo distance to the GPS satellite, the calculation amount is much smaller than that of Patent Document 1. Since the switching control means detects the presence or absence of cycle slip with the accuracy reduction index as a threshold value, it is possible to realize switching that not only makes the measurement blank period even smaller than in the prior art but also results in an optimal measurement error.

(3) The solving means 3 is the mobile station speed measuring device described in the solving means 1 or 2, wherein the acceleration measured by the acceleration sensor is time-updated by a Kalman filter and noise filtering is performed to obtain the traveling speed of the mobile station. A third speed measuring means for measuring, and the switching control means is configured so that the third speed measuring means allows the mobile station to measure the travel speed of the mobile station after the cycle slip has occurred. The gist is to perform switching control so as to measure the traveling speed of the vehicle.

  It takes time (for example, about 2 seconds) until the traveling speed of the mobile station can be measured by the first speed measuring means after the occurrence of the cycle slip. According to the solution means 3, the acceleration measured by the acceleration sensor of the third speed measurement means is obtained even during a period in which neither the first speed measurement means nor the second speed measurement means can measure the traveling speed of the mobile station. The running speed of the mobile station is measured by time update by Kalman filter and noise filtering. Therefore, even if a cycle slip occurs, the traveling speed of the mobile station can be continuously measured without a blank period.

  According to the present invention, even if a cycle slip occurs while the mobile station is moving, the traveling speed of the mobile station can be measured by reducing the time during which the speed measurement by GPS is not possible compared to the prior art.

  The best mode for carrying out the present invention will be described with reference to the drawings. The mobile station corresponds to, for example, a car or a train. In this embodiment, an example applied to a car will be described.

  FIG. 1 shows a configuration example of the present invention. The speed measuring device 20 is provided in an automobile. The speed measuring device 20 includes a receiver 21, positioning means 22, first speed measuring means 23, switching control means 24, second speed measuring means 25, third speed measuring means 26, and the like. Each means is realized by execution of software or a function of hardware configuration.

  The receiver 21 receives a carrier wave C transmitted from four or more GPS satellites 10. The positioning means 22 obtains and outputs the Doppler frequency Da, the current position Db, the accuracy reduction index Dc, and the like based on the data included in the carrier wave C received by the receiver 21. In this example, a position-related index (PDOP) is used as the accuracy decrease index Dc.

  The first speed measuring means 23 includes a Doppler speed calculating means 23a, a fusion filter means 23b, etc., receives the Doppler frequency Da output from the positioning means 22, and measures and outputs the traveling speed V1 of the automobile. The Doppler speed calculation means 23a calculates the Doppler speed based on the Doppler frequency Da. The Doppler speed calculated in this way corresponds to the observation update data. Further, the integral speed is calculated by integrating the acceleration separately from the Doppler speed, and the calculated integral speed corresponds to the time update data. The fusion filter means 23b converts the observation update data and the time update data into an optimum mixing ratio (for example, Kalman gain) according to the difference between the Doppler speed calculated by the Doppler speed calculation means 23a and the integration speed obtained by integrating the acceleration. ) To estimate the running speed V1 of the automobile and output it as a measurement result.

  The second speed measuring means 25 includes a TD method speed calculating means 25a, a fusion filter means 25b, etc., and receives the current position Db output from the positioning means 22 and measures the traveling speed V2 of the vehicle by the TD method. The TD method speed calculating means 25a calculates the moving speed based on the previous and current current position Db. The moving speed calculated in this way corresponds to observation update data. The integral speed described above is calculated separately from the moving speed (corresponding to time update data). The fusion filter unit 25b converts the observation update data and the time update data into an optimum mixture ratio (for example, Kalman) according to the difference between the moving speed calculated by the TD method speed calculation unit 25a and the integration speed obtained by integrating the acceleration. The driving speed V2 of the vehicle is estimated by combining with the gain) and output as a measurement result.

  Here, a configuration example of the fusion filter means 23b and 25b will be described with reference to FIG. FIG. 2 shows an example in which a discrete-time Kalman filter using jerk (acceleration change rate) as a drive source is used. Since the fusion filter means 23b and the fusion filter means 25b in FIG. 1 have the same configuration, here, the fusion filter means 23b will be described as a representative.

In FIG. 1, the fusion filter means 23b has the Kalman filter 30, the fusion part 32, the acceleration sensor 34, etc. of FIG. The Kalman filter 30 includes a Doppler velocity filtering unit 30a and an acceleration filtering unit 30b. The Doppler speed filtering unit 30a receives the Doppler speed (TD speed), performs filtering, and outputs the filtering speed. A discrete Kalman filter for a motion equation obtained by discretizing a continuous motion equation such as the following equation (1) for the Kalman gain K, the observation matrix H, the discrete transfer characteristic z ⁻¹ , and the transition matrix F in the Doppler velocity filtering unit 30a. Holds. The jerk ε means the acceleration change rate.

The acceleration filtering unit 30b receives the acceleration output from the acceleration sensor 34, performs integration, and outputs an integration speed. For the Kalman gain K, the observation matrix H, the discrete transfer characteristic z ⁻¹ , and the transition matrix F in the acceleration filtering unit 30b, a discrete Kalman filter for a motion equation obtained by discretizing a continuous motion equation such as the following equation (2) is provided. It holds.

  The fusing unit 32 fuses the filtering speed output from the Doppler velocity filtering unit 30a and the integration velocity output from the acceleration filtering unit 30b and outputs the result. That is, the observation update frequency of the Doppler velocity filtering unit 30a is different from the observation update frequency of the acceleration filtering unit 30b (normally, both are the same). In this example, the observation update frequency of the Doppler velocity filtering unit 30a is 5 [Hz], and the observation update frequency of the acceleration filtering unit 30b is 100 [Hz]. Therefore, interpolation is performed so as to fill the gap of the filtering speed with the integration speed, and the result is output.

  The third speed measuring unit 26 includes an acceleration sensor 26a, a speed calculating unit 26b, and the like. The speed calculating unit 26b calculates time update by a Kalman filter and noise filtering by calculating the acceleration α measured by the acceleration sensor 26a. The traveling speed V3 is measured.

  The switching control unit 24 receives the accuracy decrease index Dc output from the positioning unit 22, and the traveling speed V 1 output from the first speed measuring unit 23 and the traveling speed V 2 output from the second speed measuring unit 25. The travel speed V3 output from the third speed measurement means 26 is automatically switched to any one of the travel speeds V3 and output as a composite speed Vo. Specifically, if the accuracy drop index Dc is equal to or higher than a predetermined value (for example, 2 or 3 and can be set as appropriate), it is switched to the traveling speed V1 of the first speed measuring means 23 and output, assuming that a cycle slip has occurred. To do. However, immediately after the occurrence of the cycle slip, the traveling speed V1 cannot be output until the first speed measuring means 23 also returns, so that the traveling speed V3 of the third speed measuring means 26 is switched and output. On the other hand, if the accuracy decrease index Dc is less than the predetermined value, it is switched to the traveling speed V2 of the second speed measuring means 25 and output, assuming that no cycle slip has occurred.

  When the measurement was performed using the speed measuring device 20 configured as described above, a test result as shown in FIG. 3 was obtained. When the accuracy drop index Dc becomes significantly large at time t1 and a cycle slip occurs, both the Doppler speed calculated by the Doppler speed calculation means 23a and the TD speed calculated by the TD method speed calculation means 25a become abnormal. Therefore, the traveling speed V3 of the third speed measuring means 26 is output as the composite speed Vo (that is, Vo = V3). Thus, the state in which the traveling speed V3 is output as the composite speed Vo continues from time t1 to time t2 after elapse of 0.2 second to 4 seconds or the like (that is, the initial stage of recovery).

At time t2, since the cycle slip applied to the Doppler frequency Da ends and returns, the accuracy reduction index Dc is also somewhat reduced. Therefore, the Doppler speed calculated by the Doppler speed calculating means 23a becomes normal, and the traveling speed V1 of the first speed measuring means 23 is output as the composite speed Vo (that is, Vo = V1).
Further, at time t3 when 6 seconds to 10 seconds or the like (that is, recovery time) has elapsed from time t1, the cycle slip applied to the current position Db is completed and returned. Therefore, the TD speed calculated by the TD method speed calculating means 25a becomes normal, and the traveling speed V2 of the second speed measuring means 25 is output as the composite speed Vo (that is, Vo = V2).

According to the embodiment described above, the following effects can be obtained.
(1) Compared with the TD method, the period from when a cycle slip occurs at time t1 to when the Doppler frequency Da is obtained at time t2 is significantly shorter (see FIG. 3). The switching control means 24 switches between the first speed measuring means 23 and the second speed measuring means 25 depending on whether or not a cycle slip has occurred. Even if a cycle slip occurs while the vehicle is moving, the first speed measurement means 23 responds to the difference between the Doppler speed (observation update data) and the integration speed (time update data) obtained by integrating the acceleration. Then, the traveling speed of the automobile is measured by fusing the observation update data and the time update data at an optimum mixing ratio (for example, Kalman gain) and outputting the composite speed Vo. Therefore, even if a cycle slip occurs, it is possible to measure the traveling speed of the automobile by reducing the TD positioning value from the GPS satellite 10 or the blank period of the Doppler speed as compared with the prior art.

(2) Since the accuracy reduction index Dc (PDOP; position index) is obtained by calculation based on the approximate distance or pseudo distance to the GPS satellite 10, a considerably small calculation amount is sufficient. Since the switching control means 24 detects the presence or absence of cycle slip with the accuracy reduction index Dc as a threshold value, it is possible not only to make the measurement blank period even smaller than before, but also to realize switching that results in an optimal measurement error. .

(3) Even during the period from the occurrence of the cycle slip at time t1 to the time t2 when neither the first speed measurement means 23 nor the second speed measurement means 25 can measure the traveling speed of the vehicle, the third The speed measuring means 26 integrates the acceleration measured by the acceleration sensor 26a, performs time update by a Kalman filter, and performs noise filtering to measure the traveling speed V1 of the automobile and output it as a composite speed Vo (see FIG. 3). Therefore, even if a cycle slip occurs, the traveling speed of the automobile can be continuously measured without a blank period. Since the period from time t1 to time t2 is short, the integration error is small (approximately 0.2 [m / s] in RMS), and practicality is ensured.

[Other Embodiments]
Although the best mode for carrying out the present invention has been described above, the present invention is not limited to this mode. In other words, the present invention can be implemented in various forms without departing from the gist of the present invention. For example, the following forms may be realized.

(1) In the above-described embodiment, the first speed measurement means 23 and the second speed measurement means 25 are provided with the same fusion filter means (see FIG. 1), but a single fusion filter means 27 is provided. (See FIG. 4). In the following, the configuration example of FIG. 4 will be briefly described. However, the same configurations as those in FIG. 1 are denoted by the same reference numerals unless otherwise described.

  A speed measuring device 20 shown in FIG. 4 includes a receiver 21, positioning means 22, Doppler speed calculating means 23a, TD method speed calculating means 25a, switching control means 24, fusion filter means 27, acceleration sensor 26a, speed calculating means 26b, and the like. Have In relation to FIG. 1, the Doppler speed calculation means 23 a and the fusion filter means 27 are equivalent to the first speed measurement means 23, and the TD method speed calculation means 25 a and the fusion filter means 27 are equivalent to the second speed measurement means 25. The acceleration sensor 26a, the speed calculation means 26b, the fusion filter means 27, and the like correspond to the third speed measurement means 26.

  The Doppler speed calculation means 23 a calculates the Doppler speed Vd based on the Doppler frequency Da output from the positioning means 22 and outputs it to the switching control means 24. The TD method speed calculation means 25 a calculates the TD speed Vt based on the current position Db output from the positioning means 22 and outputs it to the switching control means 24. The switching control means 24 switches between the Doppler speed Vd and the TD speed Vt depending on whether the accuracy decrease index Dc is greater than or less than a predetermined value, and outputs it as the traveling speed Vi. However, the traveling speed Vi is not output during a period in which both the Doppler speed calculating means 23a and the TD method speed calculating means 25a cannot calculate due to cycle slip (that is, from time t1 to time t2 shown in FIG. 3).

The fusion filter means 27 has the same configuration as the fusion filter means 23b and 25b shown in FIG. The fusion filter means 27 is provided with observation update data according to the difference between the travel speed Vi (observation update data) output from the switching control means 24 and the integrated speed Vs (time update data) calculated by the speed calculation means 26b. And the time update data are merged at an optimum mixing ratio (for example, Kalman gain), and the combined speed Vo of the automobile is output as a measurement result. Note that when the switching control means 24 does not output the traveling speed Vi, the integrated speed Vs is output as the combined speed Vo of the automobile.
Even in the case of the configuration shown in FIG. 4, as in the above-described embodiment, even when a cycle slip occurs, it is possible to measure the traveling speed of the automobile by reducing the blank period compared to the conventional case. Further, the cost can be kept low by the amount of the fusion filter means being reduced.

(2) In the above-described embodiment, the Kalman filter 30 is mainly used for the fusion filter means 23b, 25b, and 27 (see FIG. 2). Instead of this form, another estimation filter such as a least square method or a linear regression equation may be used. Even when such other estimation filters are used, the filtering speed and the integrated speed can be obtained, and the traveling speed and the combined speed can be finally output.

(3) In the above-described embodiment, the position-related index (PDOP) is used as the accuracy-decreasing index Dc. However, the horizontal accuracy index (HDOP), altitude index (VDOP), and time index (TDOP) One or more may be used. Since any of the indices can be obtained with a considerably small amount of calculation, the time during which speed measurement by GPS cannot be performed can be further reduced compared to the conventional method.

(4) In the above-described embodiment, the occurrence of cycle slip is detected based on the accuracy reduction index Dc. Instead of this form, the occurrence of cycle slip may be detected based on the rate of change of one or both of the Doppler frequency Da and the current position Db output from the positioning means 22. If a cycle slip occurs, it becomes impossible to receive a carrier wave, and the values of the Doppler frequency Da and the current position Db calculated by the positioning means 22 are greatly changed from those before the occurrence. Therefore, if the rate of change becomes equal to or greater than a certain value, it is configured that the switching control means 24 performs switching assuming that a cycle slip has occurred. According to this configuration, it is possible to obtain the same effect as that of the above-described embodiment without using the accuracy decrease index Dc.

(5) In the above-described embodiment, the speed measuring device 20 is applied to an application for measuring the speed of an automobile. It can replace with this form and can also be applied as a precision speed sensor of a driving robot or a precision speed sensor of auto cruise. Even in such an application, the same effects as those of the above-described embodiment can be obtained.

It is a block diagram showing the example of a structure of this invention. It is a block diagram showing the structural example of a fusion filter means. It is a chart figure showing the example of measurement performed using the speed measuring device. It is a block diagram showing the other structural example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 GPS satellite 20 Speed measuring device 21 Receiver 22 Positioning means 23 First speed measuring means 23a Doppler speed calculating means 23b, 25b, 27 Fusion filter means 24 Switching control means 25 Second speed measuring means 25a TD method speed calculating means 26 First 3 Speed measurement means 26a Acceleration sensor 26b Speed calculation means 30 Kalman filter 30a Doppler speed filtering section 30b Acceleration filtering section 32 Fusion section 34 Acceleration sensor C Carrier wave Da Doppler frequency Db Current position Dc Accuracy reduction index V1, V2, V3, Vi Traveling speed Vd Doppler speed Vt TD speed Vs Integral speed Vo Composite speed α Acceleration

Claims (3)

A mobile station speed measuring device comprising a receiver for receiving a carrier wave transmitted from four or more GPS satellites, and measuring a traveling speed of the mobile station based on data included in the received carrier wave,
Positioning means for obtaining and outputting the Doppler frequency and the position of the mobile station based on the data included in the carrier wave;
First, the traveling speed of the mobile station is measured by fusing with the optimum mixing ratio according to the difference between the Doppler speed calculated based on the Doppler frequency output from the positioning means and the integrated speed obtained by integrating the acceleration. 1 speed measuring means;
A second speed measuring means for measuring the traveling speed of the mobile station by a TD (Time Differential) method based on the position of the mobile station output from the positioning means;
After the cycle slip occurs, the initial stage of recovery from the cycle slip measures the traveling speed of the mobile station by the first speed measuring means, and when the cycle slip does not occur, the traveling speed of the mobile station by the second speed measuring means. A mobile station speed measuring device comprising switching control means for performing switching control so as to measure the frequency. A mobile station speed measuring apparatus according to claim 1,
The switching control means obtains an accuracy decrease index related to the arrangement of the GPS satellites, and when the accuracy decrease index exceeds a predetermined value, measures the traveling speed of the mobile station by the first speed measurement means, and the accuracy decrease index A mobile station speed measuring device that performs switching control so that the second speed measuring means measures the traveling speed of the mobile station when the value is less than a predetermined value. A mobile station speed measuring device according to claim 1 or 2,
A third speed measuring means for measuring the traveling speed of the mobile station by updating the time measured by the acceleration sensor using a Kalman filter and noise filtering;
The switching control means measures the traveling speed of the mobile station by the third speed measuring means while the cycle slip is occurring, and measures the traveling speed of the mobile station by the first speed measuring means at the initial stage of recovery from the cycle slip. Then, the mobile station speed measurement device performs switching control so that the second speed measurement means measures the travel speed of the mobile station when the accuracy decrease index becomes less than a predetermined value.

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